Research category
Quantum Information
What can be transmitted, recovered, and transformed when information is encoded in quantum states?
The field in perspective
Quantum information makes physical constraints into quantitative tasks. How many entangled pairs can two laboratories extract? How much unknown quantum information can a noisy channel transmit? Which correlations survive losing part of a system?
The same density matrix can support different operational questions. Each page states the allowed operations and resources before assigning an information quantity or a limit.
Fundamental questions
- Is entanglement a reversible resource?
Pure-state entanglement has a clean asymptotic currency. Mixed states reveal irreversibility and limits to that description.
- How much quantum information can noise transmit?
Quantum channel capacity requires both a coding strategy and a converse bound; optimizing one use is not generally enough.
- When is lost quantum information recoverable?
Recovery depends on what the environment learned, not simply on whether a noisy transformation has an algebraic inverse.
- What can three particles share that two cannot?
A third particle removes the Schmidt decomposition, so tripartite entanglement comes in kinds rather than amounts. For three qubits the genuinely tripartite pure states fall into two classes that no local protocol interconverts.